How can I make the decoration to take the shape of any object
You can achieve this effect with the Shrinkwrap modifier as long as the pattern you are trying to apply is a mesh. For this to work best you should create a volume of your pattern, preferably spherical, then apply the shrinkwrap modifier with the "project" setting.

I would suggest keeping the pattern flat, then adding the thickness after it has shrinkwrapped around the object (possibly with the solidify modifier).

An alternative is also the Cast modifier, however this works only on geometric objects like spheres or tubes.